calcium-activated potassium channel activity

Definition

Target type: molecularfunction

Enables the calcium concentration-regulatable energy-independent passage of potassium ions across a lipid bilayer down a concentration gradient. [GOC:dph, GOC:mtg_transport]

Calcium-activated potassium channels (KCa channels) are a diverse group of ion channels that are activated by an increase in intracellular calcium concentration. These channels play critical roles in a wide range of physiological processes, including neuronal excitability, muscle contraction, hormone secretion, and cell volume regulation. The molecular function of calcium-activated potassium channel activity can be summarized as follows:

1. **Calcium Sensing:** KCa channels possess a specific calcium-binding domain, typically located within the channel's cytosolic region. This domain binds calcium ions, triggering a conformational change in the channel protein.

2. **Channel Opening:** The binding of calcium to the channel's calcium-binding domain leads to a structural rearrangement, resulting in the opening of the channel pore. This allows potassium ions to flow across the cell membrane, down their electrochemical gradient.

3. **Potassium Conduction:** Once the channel is open, potassium ions permeate through the pore, moving from the intracellular compartment to the extracellular compartment. This outward movement of potassium ions can have several physiological effects.

4. **Membrane Potential Regulation:** KCa channels contribute to the regulation of membrane potential by increasing potassium permeability. By allowing potassium ions to flow out of the cell, these channels hyperpolarize the membrane, making it less likely to fire an action potential.

5. **Cellular Signaling:** KCa channel activity can influence cellular signaling pathways by modulating the activity of other ion channels, enzymes, or second messenger systems. This can affect various cellular processes, including neuronal communication, muscle contraction, and hormone secretion.

6. **Cell Volume Regulation:** KCa channels can play a role in cell volume regulation by contributing to potassium efflux. This efflux can lead to water efflux, reducing cell volume.

7. **Modulatory Effects:** The activity of KCa channels can be modulated by a variety of factors, including phosphorylation, membrane potential, and interactions with other proteins. This allows for fine-tuning of channel activity in response to different cellular needs.

In summary, calcium-activated potassium channels are essential for maintaining cellular function by regulating membrane potential, contributing to cellular signaling pathways, and regulating cell volume. Their diverse molecular functions make them crucial players in a wide range of physiological processes.'
"

Proteins (7)

Compounds (12)